1. Field of the Invention
The present invention is directed to the field of grenades, and more specifically to a safety fuze for use with hand grenades.
2. Related Art
The hand grenade presently in use by the U.S Department of Defense is the M213, shown in U.S. Pat. No. 2,562,928 to Lewis. The hand grenade fuze 8 incorporates a number of features standard in hand grenades and similar, hand thrown, fuze-activated devices. For example, a safety pin or pull ring assembly 100 is inserted through the lever 92, through apertures in the fuze body 12, over the striker assembly 70 to restrain the striker assembly 70 in the safe position. Also, a safety clip (not shown) commonly is fastened around the lever 92 and an extension (not shown) of the fuze body 12 to prevent accidental, premature release of the lever 92 and the striker assembly 70 if the pull ring assembly 100 was accidently removed.
However, in military situations when silence is of the utmost importance, the user frequently employs the unauthorized, unsafe, procedure of removing the safety clip to avoid detection by the enemy given by the distinctive sound from its removal, or the noise it produces upon impacting objects after being discarded. Also, because of the short length of the striker assembly 70, if the lever 92 is unknowingly released even a slight amount after the pull ring assembly 100 is removed, the striker assembly 70 will be allowed to rotate and the firing pin 84 will hit the primer 28, initiating the firing sequence. As this can occur without the knowledge of the user, the grenade can function while still in the user's hand or attached to an article of clothing.
Most fuze assemblies for hand grenades and the like employ lever and striker assemblies similar to those of the M213. Examples of such assemblies are disclosed in U.S. Pat. No. 2,042,461 to Gibson et al.; U.S. Pat. No. 2,421,672 to Short; U.S. Pat. No. 2,911,913 to Suden; and U.S. Pat. No. 4,513,667 to Caruso.
Another safety problem encountered with the M213 is associated with the firing train assembly; the primer assembly, the delay charge/cavity, and the detonator assembly. In the M213, the detonator charge is in direct fluid communication with the delay charge/cavity in the fuze body stem, and the delay charge/cavity is in direct fluid communication with the primer assembly. An insufficient amount of delay charge can cause a grenade to function, after the firing train has been initiated, in a shorter time than that required of complete delay charge. Also, the absence of any delay charge in the delay cavity can cause an instantaneous functioning of the grenade after the firing train has been initiated. Also, a crack or cracks, or porosity having fluid communication between the interior stem cavity and the outer stem wall of the fuze body, can permit hot gasses to be in like fluid communication with the interior of the detonator assembly. Also, the through fluid communication within the components of the firing train can cause deterioration of the explosive or pyrotechnic components, shortening shelf life and endangering the user who is depending on reliable performance of the device.
Other fuzes for hand grenades employ primer, delay, and detonator assemblies similar to those of the M213, as shown by U.S. Pat. No. 4,383,470 to Assman.
Our U.S. Pat. No. 4,926,752, which is incorporated herein by reference in its entirety, addressed these problems by the provision of a safety fuze for a hand grenade comprising a fuze body, a delay case assembly, a detonator assembly, an initiator lever assembly, a cover assembly, and a pull ring assembly. The delay case assembly comprises a delay case matingly received in the bore of the fuze body stem and has a primer portion adjacent the top and a delay portion adjacent the bottom, a sealant separating the primer portion from the delay portion, a primer positioned in the primer portion, a penetration charge positioned at the bottom of the delay case, a delay charge positioned above the penetration charge, an ignition charge positioned above the delay charge, and an air gap separating the primer portion from the ignition charge.
The detonator assembly of our '752 patent comprises a detonator case which matingly receives the fuze body stem at the top thereof and is in sealing engagement with raised crimped surfaces on the fuze body. An explosive detonator charge is positioned at the bottom thereof. A gap is provided between the fuze body stem bottom and the explosive charge.
In the embodiment shown in FIG. 4 of our '752 patent, the initiator lever assembly is mounted on the fuze body and is rotatable between an unprimed position and a primed position. It comprises an elongated initiator lever mounted at its proximal end to the fuze body head for rotation about a axis perpendicular to its plane of symmetry; a spring for biasing the initiator lever in its primed position; and a firing pin formed integrally with the initiator lever, the firing pin being positioned on the initiator lever to engage the primer when the initiator lever assembly is in its primed position. The initiator lever has such a length that in its primed position, its distal end extends forwardly of the front wall of the fuze body head. The initiator lever is longer than and extends below the cover assembly and defines a handle for holding and throwing the grenade.
The cover assembly of the embodiment shown in FIG. 4 of our '752 patent covers the top and back of the fuze body head and includes a pair of opposed pin-receiving apertures in registration with apertures in the side walls of the fuze body head. A safety latch is mounted on the cover assembly. The safety latch is movable between a first position for retaining the initiator lever in its unprimed position by engaging the apertures in the side walls of the fuze body head and a second position for permitting movement of the initiator lever into its primed position.
The pull ring assembly of the embodiment shown in FIG. 4 of our '752 patent has an elongated retaining pin adapted to be inserted through the apertures in the cover assembly and the side walls of the fuze body head. The retaining pin retains the initiator lever in its unprimed position when inserted through the apertures.
Although the fuzes disclosed in our '752 patent are effective in solving the problems present in the prior art, it was found that the seals in the detonator case assembly were unable to pass the extremely rigid MIL-STD-331 Vacuum-Steam-Pressure Test 106.1 imposed on grenade fuzes by the engineering agency at ARDEC, Picatinny Arsenal, N.J.
In addition, we found that an additional safety mechanism to prevent the unintentional arming of the grenade might be desirable. In the embodiment shown in FIG. 4 of our '752 patent, the pull ring assembly was the only mechanism that prevented an individual from rotating the safety latch, which would permit release of the initiator lever.
Further, we found that it would be desirable to modify the fuze body and the delay case assembly disclosed in our '752 patent so that the delay case assembly is usable as a reusable replacement for the M228 single-use practice fuze presently in use by the U.S. Department of Defense.
It is the solution of these and other problems to which the present invention is directed.